It is part of the historic collections of Burton Constable Hall, with whom Temple Newsam House and Leeds Museums and Galleries has a close working relationship. It has recently been at the Leeds Museum Discovery Centre so that Matthew Read, clocks programme tutor at West Dean College, could inspect and assess it for Burton Constable’s curatorial team. It requires conservation treatment and will be a likely candidate for a PRISM grant.

Exquisitely made, one wonders how they were able to achieve such incredible fineness and accuracy. It was made to measure transits of heavenly bodies such as the moons of Jupiter, Venus etc. All part of the star mapping, astronomy, navigation, map-making endeavour, gentlemen scientists around the UK, such as William Constable, undertaking their observations and sharing them. It is missing its drive motor entirely, however. It would have been essentially a clock mechanism, weight driven, and pendulum controlled, that compensated for the rotation of the Earth, to allow the telescope to track the transit with the factor of the Earth’s rotation removed from the equation. Telescopes of these types were mounted parallel to the equator.

Interesting fact: the cross-hairs on graticules of this period are made from spider silk. A graticule is simply a piece of thin glass with reference marks on it, usually a grid, in order to have fixed references to measure against. They are needed in telescopes and microscopes if one is trying to measure a distance, or movement. In the store at Leeds Museum Discovery Centre we had for a time together two items representing the white heat of 18th century technology, this telescope and the Harrison clock. They were both cutting edge stuff, the rocket science of that time, one for mapping the heavens, the other for precision timekeeping.